1. Technical Field
The present invention relates to an illumination device used in an electro-optical device such as a liquid crystal display device.
2. Related Art
An electro-optical device, such as a liquid crystal display device, allows color display by using an illumination device that emits white light, and a display panel equipped with three color filters of red (R), green (G), and blue (B), such as a liquid crystal display panel. The illumination device transmits the emitted white light through the display panel to illuminate the display panel. Such an illumination device includes a plurality of light sources for emitting light of RGB colors, such as light emitting diodes (LEDs). The illumination device emits white light by combining the RGB light emitted from these light sources.
However, if LEDs are used as light sources and are turned on by causing a constant current to flow through the LEDs, heat loss occurs in the LEDs. The heat loss may reduce the life of the LEDs. JP-A-2004-93761 discloses a technique in which LEDs for RGB colors used as light sources of an illumination device are illuminated on a time-division basis, thereby reducing the power consumption and extending the life of the LEDs.
When illumination devices are combined with display panels to form electro-optical devices, in even the same illumination device, different color reproduction regions on the display screen are obtained depending on the display panels used with the illumination devices. In order to realize a desired color reproduction region on the display screen, it is necessary to adjust the illumination colors of the illumination device in consideration of the characteristics of the display panel. JP-A-2004-93629 discloses a technique in which the pulse width of a current flowing through each of LEDs for RGB colors to illuminate the LEDs on a time-division basis is changed, thereby adjusting the chromaticity on the display screen. JP-A-2005-56842 discloses an assembly having both an LED for emitting white light and an LED for a low-brightness light color, in which the color production on the display screen is improved.